The Science of the Timelords
by thisisforyou
Summary: In which Sherlock discovers that even his heart is bigger once you're on the inside. Post-Reichenbach, post-Amy, Sherlock and the Doctor meet at a dodgy bank-robbery in Frankfurt and decide that being alone is easier when you have someone to do it with. So begins the adventure of a lifetime in which the Doctor tries not to worry about the fact that Sherlock Holmes is fictional.


**A/N: **Quick note on timelines before we start: this is set three years post-Reichenbach in Sherlock's timeline and after The Angels Take Manhattan in the Doctor's. I started writing it before Clara but so far I haven't contradicted anything in the Snowmen, so it could be post-Clara if you prefer. I'll give a proper introduction to my intentions at the end of the chapter.

Thanks for reading!

-**for you!**

* * *

Sebastian Moran clutched at the bloody remnants of his left arm and glared mulishly up at the barrel of the gun in front of his face. Sherlock lifted a condescending eyebrow. "You're hardly in a position to be stubborn, Colonel," he said idly, focussing all of his energy on stopping his hand from shaking. John's hand wouldn't have shaken. He watched with implacable face while the ex-Colonel drew in a shuddering breath and spat at his feet. He quirked an entirely mirthless grin. "Suit yourself," he said coldly, and pulled the trigger.

After, he threw the Glock in a skip and sat down at a bus stop with his head resting in shaking hands. A mother herding three children took one look at him and pushed her charges across the street; Sherlock watched them send furtive glances back at him and sighed. He didn't blame them. His Spencer Hart slacks were ripped at the knees and splattered with Moran's blood: he looked a mess. He _felt_ a mess. And he wanted to go home.

A bus pulled into the stop; he shook his head at the driver and it took off again, screeching tiredly. Sherlock stood up. He'd told himself, tided himself over to finish the job that needed to be done by telling himself that when it was over he could go back. And yet… Mycroft sent him photos yesterday. John had been laughing in the park with Lestrade and his daughter, sitting at a candlelit table with a bubbly-looking redhead, chatting happily with Sarah in the waiting room of the clinic. He'd known it would happen eventually, and yet facing up to it would never get any easier: John had moved on.

Sighing heavily, feeling as though every step carried him through treacle, he set off down the street towards the centre of Frankfurt. It was not where he had pictured spending so much of his time, but Mycroft had recommended it to him as a base for safekeeping. The bank – the _Kreditanstalt für Wiederaufbau_ – had been rated the safest in the world, and he needed his identity safe.

The bank was moderately busy for the end of the day, but its reputation preceded it, so Sherlock dismissed it; the group of people sitting by the door in full-body suits and tinted fishbowl helmets he gave a second glance. It was odd, given the heat of the day. Even the most eccentric of the Frankfurt nightlife usually abandoned the mock-armor in summer.

The counter on the left bore the sign _English_ in obnoxiously large writing; Sherlock made his way towards it, still shaken and too tired to summon his German for the exchange. "Peter Guillam," he said curtly to the young man at the counter. "I'd like to withdraw the contents of my safe-deposit box."

The man intoned the customary, most likely scripted response. Evidently it had been a long and monotonous day. For a moment Sherlock almost envied him.

His passports were there, nestled between photographs and bank notes and the other memorabilia he had managed to salvage from the flat: the picture Mrs Hudson had snuck on them one Christmas where Sherlock was leaning over John's shoulder to read the card Molly had sent and the both of them were smiling, unaware of being watched, a perfect moment Sherlock kept in his mind for the bitterest of the cold nights. He looked like a different person in his passport photos, and the name _Sherlock Holmes_ sounded strange spoken in his own mind.

He could go back. He had promised.

And yet… Sherlock pictured lighting a fire in the grate at the flat he'd rented downtown and throwing the box inside, watching the smoke curl in lazy spirals from the tatters of his old life. He'd keep the photograph, frame it perhaps and keep it on the mantel of the flat he kept wherever he might end up. John would never know. And eventually, perhaps, Sherlock would move on.

He emptied out the contents of the box into the cheap duffel-bag the bank provided him with, handed one of the bank-notes back to the teller, and made to leave.

Only to find the glass door of the bank blocked by the spacesuit-wearing fanatics.

"Oh, for God's sake," Sherlock huffed. "Get out of my way." The people in the suits didn't move; Sherlock looked them up and down. Difficult, perhaps, to deduce a person when all he could really see of them was their full-body suit, although their posture suggested determined, possibly military bearing. "Oh," he said, feeling something ugly and fed up flood the pit of his stomach. "You're going to try and hold this place up, aren't you? You do know this is the most secure bank in the world."

The few people milling about in the lobby had turned to see what was going on, and Sherlock heard a few frightened murmurs and a muffled scream. He frowned as the suited robbers didn't move. "Right," he said decisively. He refrained from rolling up his sleeves, but the gesture would not have gone amiss as he took a deep breath. "I've never seen an outfit like that before, but you can't possibly wear it just for fun, so they've been designed or at the very least procured for this specifically: you're almost definitely not in this for the money – what is it, the challenge? I'd say you're _professionals_, but you've miscalculated, because _no-one_ walks around Frankfurt in an outfit like that and you've already got yourself noticed, it'll be easy for the authorities to track down who made the suits for you, so I'd say you're not from around here. Very definitely not from around here – in fact, I might even go so far as to say that you're completely alien."

To punctuate that last word, he reached forward and pressed a promising-looking red button on the front of its outlandish outfit, and the black fishbowl-type apparatus slid backwards. The group behind him let out a collective gasp.

It was indeed alien. Sherlock tried not to visibly react to the fact that the thing looked incredibly like a rhinoceros someone had trained to walk on its hind legs and squeezed into a spacesuit and carry on with his deductions. He'd been on a roll. "So," he continued briskly. "Safest bank in the world, I'm assuming that's not a coincidence. Money you could get much easier from somewhere else, and hardly anyone keeps money here anyway. No, there are far more important things in these safe-deposit boxes. What is it, then? The Jewel of the West? The beryl coronet? Some sort of Nazi relic?" the rhino remained impassive. Sherlock narrowed his eyes. "No," he breathed slowly, tilting his head critically. "There must be something else. Something you think I don't know about, something you think _no-one _knows about."

"You're a regular Sherlock Holmes, aren't you?" a voice behind him said brightly. Sherlock spun around; leaning against a till was a skinny young man with a bow-tie and an innocuous, boyish grin.

"Excuse me?"

The man pushed off the counter, his face momentarily turning gloomy. "Oh, of course. It's what, 2015? Nobody knows who Sherlock Holmes is anymore, do they."

Sherlock frowned heavily. "Of course I know who Sherlock Holmes is," he argued, nonplussed. The man sounded British – had he been there when he'd been the most popular face on the news? Mycroft had told him about the media storm after his departure.

The newcomer, however, looked delighted. "Do you? Wonderful! Good to know people still remember the classics. Childhood hero?"

"What? What do you mean, 'the classics'?" Sherlock rounded on the man in irritation. "I _am_ Sherlock Holmes."

The young man laughed. "Oh, dear. I do have a way of picking them, don't I?" When Sherlock continued to frown in utmost confusion, his grin disappeared. "Oh. _Oh._" He clapped his hands in delight. "Oh. Oh, brilliant. I'm talking to Sherlock Holmes." He ran a hand through his floppy hair. "You're not wearing the hat," he said, as though that explained everything.

It'd been years since he'd heard that, and the old gripe almost made him smile. "Why does everyone go straight to the hat? It wasn't my hat."

The man chuckled again, sounding delighted. Sherlock wasn't quite sure what his game was, but the constant flattery was softening him to such an extent that he was mildly suspicious. "I'm the Doctor," he said, sticking out a large hand proudly. "There are more dignified ways I could have done that, but you caught me by surprise."

He had large, solid hands; Sherlock shook the one he'd offered gingerly. "The Doctor," he repeated incredulously. "Doctor who?" he stared at the man for a moment: he wasn't being deliberately evasive, but he chuckled at the question like he heard it all the time. "Just _the Doctor_," Sherlock concluded, deciding not to question it. "All right."

The Doctor grinned again. "Sorry. Can't tell you my real name – by law, actually - and you wouldn't be able to pronounce it if I could."

Sherlock lifted an eyebrow. "You think so?"

"No, I know you wouldn't," the man said offhandedly. "It wasn't made for the human tongue, there are sounds in it you physically couldn't produce."

Right. "Okay. So you're not human either. Since you're here and you seem to be on my side, I'm assuming you know what to do about the aliens that aren't?"

The Doctor looked briefly past him at the rhino things and made a few guttural, single-syllable noises. Sherlock watched in surprise as the thing grunted back. "So you're okay with them being alien and illogical and all that, then? Most people try to deny it," the Doctor commented.

Sherlock frowned at him. "Of course. When you have eliminated the impossible, whatever remains, however improbable –"

"Must be the truth," the Doctor finished, nodding excitedly as though he was expecting that exact phrase.

Slightly startled, Sherlock nodded briskly. "Exactly. So." He looked at the Doctor expectantly. "What kind of extra-terrestrial item would someone want to hide in a place like this?"

The lanky man, looking startled to be addressed, shrugged bewilderedly. "I don't know!" he exclaimed, his voice almost affronted. "It could be anything! You're Sherlock Holmes, you figure it out!"

He blinked. "How am I supposed to do that? A potter can't be expected to make pots without clay, and a detective can't make deductions without facts. You seem to be the man with the facts at the moment, so I asked you. Fat lot of good _you_ were." The Doctor shrugged, looking thoroughly unapologetic and still watching Sherlock as though expecting him to do something incredible. It was a look he hadn't received in three years, and it made Sherlock want to _do_ something incredible in return. "Maybe _they'll_ be more help," he said scathingly, turning to the rhinoceros. "What do you want?" he asked.

The rhino shifted brutishly. "Remain calm," it said in a monosyllabic grunt. "We have no wish to harm you."

"Clearly," Sherlock told it, folding his arms. "Otherwise I'd already be dead, I've held you up enough."

"Actually," the Doctor interjected, "they _can't_ harm you. Earth is neutral territory, they don't have jurisdiction."

Sherlock turned to look at him. "_Jurisdiction_? So they're what, police?"

The Doctor shrugged. "They're called the Judoon, they're more like hired thugs. They call themselves police, but really they work for the highest bidder."

He nodded judiciously. "Right. I'd guess these ones are like a band of rebels, or something, otherwise they wouldn't dare do _anything _without jurisdiction. Does that sound right? They look pretty gormless." The Doctor shrugged, still looking amused. "So. Maybe the bank would know." He spun around quickly, approaching the skinny, terrified-looking man behind the English-speaking counter. "Can we see the manager, please? It's important. These _things_ pose a serious danger to the bank's security."

The man shied away from him. "The manager's not here," he said helplessly. "No-one is, it's too late in the day. There's just us."

Sherlock growled in frustration. "Fine. Give me access to the computer."

"I can't! I don't know who you are, you could be in league with them –"

The Doctor stepped in behind him, crowding against his back. "Let me, then. John Smith, national Inspector of Government banking. Was here to do a spot-check, got a bit sidetracked."

With a suspicious look at the fold-out badge the Doctor was holding out at him, the teller stepped back and gave them access to the computer. Sherlock surged forwards towards it, but was beaten to it by the floppy-haired man, whose fingers flew across the keys as though he did it every day. Slightly put out, Sherlock leaned against the counter and tried to draw the Doctor's attention to the fact that the Judoon were marching towards and past them, pushing the other tellers out of the way to move into the belly of the bank. "It'll be password protected," Sherlock said sceptically. "The information you're trying to access. If you give me a moment, I should be able to figure it out."

A pop-up password box flashed up; Sherlock smirked. The Doctor grinned boyishly at him and whipped something that looked almost like a pen from his top pocket. "Not to worry," he said brightly, and pointed the device at the computer. It made a sort of buzzing noise and the password box disappeared, replaced instantly with a floor-plan of the bank building and what looked like the feed from the cameras in the vault. Sherlock blinked.

"What _is_ that?" he asked indignantly. "And that piece of paper you had before, that wasn't _bank_ ID. If I had to guess, I'd say it shows whatever you want it to. How does it work?"

The Doctor grinned. "It's slightly psychic."

Sherlock frowned. "_Psychic_ paper," he repeated. "And that thing? Operates by sound, am I right? Like sonic waves?"

"Yep," the Doctor threw over his shoulder, still tapping at the laptop and trying to zoom in on the plans. "It's a Sonic Screwdriver." He looked up at Sherlock, then, frowning slightly in amazement. "My _word_, you're clever."

He smirked a little, because it had been years since anyone had called him clever and he'd almost forgotten what it felt like. "So, what have you got, then, _Doctor?_" he asked.

The alien grinned broadly at him and tapped a few more keys. "The plans all look fine," he said, gesturing towards them. "Except for _this_ staircase icon here, because there aren't registered vaults down there and actually, this is 21st-century Frankfurt, they're not _allowed_ to tunnel under this street. So clearly someone's been up to something." He brought back the camera feeds to show the room that was supposed to have the staircase; it was lined with banks of safe-deposit boxes, but Sherlock couldn't see any kind of trapdoor or hidden entrance. It didn't look like there was anything in there at all. Except…

"There's something wrong with that," Sherlock mused, leaning over the Doctor's shoulder. "That back wall, something I can't quite pin down."

The Doctor shrugged, nearly causing Sherlock to bite his tongue. "Perception filter," he said lightly. "As long as you're not looking for a staircase or a door you won't see one. Once you know it's there the filter won't work. I'm going to hazard a guess and say that the Judoon are fully aware of it."

"Can they get in?" Sherlock asked.

The Doctor's broad face tilted to one side, then the other, considering it. "Safest bank in the universe? It'll probably take them about twenty minutes to get into that room. Not sure what other protection is on or beyond the perception filter."

"The _universe_?" Sherlock clarified. With the kind of technology that the Doctor was carrying – psychic paper and sonic technology – and the fact that there were inter-galactic travellers at all, Earth couldn't possibly be the most advanced planet out there.

Green-grey eyes beamed fondly at him. "Humans," the Doctor said with an almost paternal air. "You're so worried that other people are out to hurt you, so paranoid about losing your things that your safe technology is the most advanced in the universe when you haven't even developed interstellar travel yet."

Sherlock frowned. "But it's only going to take them twenty minutes to get in?"

"Well," the Doctor said, his fingers flying over the keys again. "When I said it was the safest bank in the universe, more than half of its safety is in its location. Nobody actually knows where Frankfurt, Earth _is_, and those that do wouldn't dare take hostile action against a level five planet that hasn't made interplanetary contact. The Judoon are already here, so that's that line of defence down. Beyond that, Earth banking isn't equipped to deal with the sorts of technology the Judoon can get their hands on." He shook his head without pausing in his typing. "_God_, you're lucky I'm a genius."

He couldn't stop himself from laughing incredulously. It wasn't like he was averse to boasting when it was deserved, but the only things he'd seen the Doctor do so far was follow simple computer coding and use superior technology. "Yeah?" he asked sarcastically.

"Uh-huh," the Doctor confirmed absently. "Because, I'm going to do something very clever."

Sherlock smirked. "Are you? What might that be, then?"

The Doctor flapped a hand dismissively. "I don't know yet, but I'll think of it in a minute. One thing at a time. We need to get in there first – if I'm by the perception filter I can change something, strengthen it, stop them from getting in."

"Well, you're in the mainframe, you can control the security. Except that we can't physically get in there without letting them in as well." There was a pause; evidently the same idea had occurred to the Doctor, who was frowning mightily. "Whoever commissioned that extra room must have some way to control their security. There must be a secondary security system. Maybe an extra password encrypted somewhere?"

A soft mumbling noise came from the Doctor, who pulled out the sonic screwdriver again and aimed it at the computer. Sherlock frowned, but whatever it was it seemed to work; the screen flickered and changed, the black coding box appearing and shifting through commands at blinding speed. "There we go," the Doctor said brightly, tucking the screwdriver back into the inside pocket of his tweed jacket and tugging sharply at his bowtie. "Now, let's see… automatic relock system, secondary charges placed against each corner of the – oh!"

Quickly and with a sharp intake of breath, the Doctor pulled his hands away from the keyboard and held them in the surrender position on either side of his head. Sherlock glanced behind him in case there was someone he'd missed holding a gun to his head, but there was nothing. "What?" he asked.

"I can get the door open or keep it shut against the Judoon, but it's encrypted in Old Atraxi. It's a trip system. If I get even one character of the coding wrong, the entire tunnel explodes and collapses and whatever's in there is burned and destroyed."

Sherlock raised an eyebrow. "Maybe you should just blow it. It could be dangerous, especially with that much security. Wouldn't it be better to destroy it and not find out what it was than let them take it and run the risk that it's something you wouldn't want in the wrong hands?"

The Doctor frowned. "Not if it's some kind of national treasure and I'm going to get hauled in front of the Shadow Proclamation for blowing it up."

He didn't ask who the Shadow Proclamation were. They sounded something like the UN. "Well, then," he said lightly, leaning against the desk. "Lucky for us you're a genius, isn't it?"

The man narrowed his eyes, knowing full well Sherlock was being facetious. "You don't think I can do it," he said.

Sherlock shrugged. "I don't know what you're capable of," he replied easily. "But everything impressive you've done so far has been down to your technology rather than your brain."

The Doctor gave him a look of pure challenge. Sherlock smiled brightly as the alien flexed his fingers out in front of him, then winced when the knuckles cracked as though he hadn't expected it. Recovering, less a fair amount of dignity, his fingers hovered nervously over the keyboard. "Okay," he muttered nervously. "Old Atraxi override commands. Haven't done this in centuries, can't afford to be rusty. I can do it."

Sherlock shifted over to the next computer terminal and tapped it into life. "That sonic thing, Doctor," he asked, bringing up the password screen. "Does it only work for you?"

"No, it's just a bit complicated," the Doctor told him, briefly glancing down at it and fiddling with some kind of control. "Here."

Sherlock caught it deftly as it was thrown at him and aimed it at the computer, mimicking the Doctor's earlier movements. He made a noise of delight as the password box blinkered out of the way, replaced by the camera feeds to the vaults as the Judoon marched past. He narrowed his eyes. "They're using some kind of device to override the iris recognition software," he told the other man as he watched. The Judoon had reached the door and attached something spiderlike to the many combinations on the door. As he stared at them through the monitor, the door shuddered and then opened. "You might want to rethink your estimate of twenty minutes, Doctor," he said lightly. "If they get through the other two doors that quickly I'd say you've got less than five."

"I'm doing it!" the Doctor shouted as though he had been caught napping when he was supposed to be cleaning. "I've got past the security protocols, now I'm trying to figure out how to deadlock the door when they get there."

The next door surrendered to whatever equipment the Judoon were using. Sherlock frowned. "Well, you'd better work faster, they're almost there."

The Doctor glared at him for a moment before turning back to the computer, mumbling nonsense syllables that Sherlock assumed were Old Atraxi coding phrases. He tracked the Judoon's alarmingly fast march through the vaults of the safest bank in the universe and hoped that the Doctor would get his programming languages sorted in time. Although… he couldn't deny that he was curious as to what was inside there. Was it, as the Doctor had mentioned, some kind of jewel so precious that somebody would hide it on _Earth_? Or was it some kind of revolutionary technology? Either way, his blood hummed at the intrigue. He hadn't felt like this in years and he couldn't help the sudden rush of affection for this _Doctor_, who had looked at him like John used to and drawn him into the game so eagerly.

"Last door, Doctor," he said, still watching the other man lazily. The Doctor waved a hand at him with a vague noise. Sherlock found a smile spreading across his face and squashed it before it got any grand ideas.

Finally, the alien gave a triumphant shout. "Got it! The door should be deadlocked. It won't keep them forever, but hopefully it'll give us enough time to get down there and send them packing."

Sherlock raised a languid eyebrow. "Very good, Doctor," he drawled. "_If _it works, it will have been a very fast bit of thinking."

The Doctor seemed delighted by the news. "Ha!" he exclaimed gleefully. "Sherlock Holmes just called me clever."

"_If_ it works, I said," Sherlock admonished, but he couldn't keep back the smirk at the expression of pure joy on the other man's face. His opinion really seemed to count for something in this man's mind – this _alien's_ mind. What had he done to be recognised on an _interplanetary_ scale? "Oh – here's the test."

The Judoon had reached the bottom vault and were crowded around the back wall. The Doctor peered over Sherlock's shoulder for a moment – so used to being impressively tall, Sherlock was surprised to note that they were almost of a height – and then he snorted in amusement.

"Tell you what," he said, moving back to his own computer, where the Old Atraxi coding box was still on the screen, "we could make it really hard for them. Trigger the door to close every time they open it."

Sherlock snorted automatically at the idea. "If you think you can," he said, tipping his head to the alien. The Doctor gave him a boyish grin and turned back to the screen.

"I can do anything," the Doctor said brightly, cocking his head confidently and staring at the computer screen. Sherlock lifted an eyebrow and tried not to smile. The alien was so cheerfully cocky he almost made Sherlock believe him.

So he turned back to the monitor, watching as the Doctor tapped and the Judoon placed their device against the back wall. Something – the Doctor's _perception filter_, Sherlock gathered – shimmered and shifted, until a door in the back wall winked into existence. Sherlock blinked. It looked like something he'd seen in a film he barely remembered watching with John, all steel doors like an elevator and blinking lights all around. The Doctor hummed in the back of his throat. "And… open," he said slowly. Sherlock couldn't suppress a wry smile as the doors slid open easily. "And _closed_," the Doctor continued, tapping out a distinctively short sequence at the computer. Sherlock almost laughed as the Judoon looked at each other; he didn't think their rhinoceros-like faces could register puzzlement, but their postures were doing a fine job of it.

The Doctor tapped his fingers impatiently against the desk. "Come on, hurry up, try again," he muttered. Sherlock rolled his eyes when the alien shot a wide, boyish grin in his direction. Were he not desperately enjoying this himself, he would have commented on the apparently-unhealthy enjoyment the Doctor was getting from torturing this band of obviously lesser life-forms. "There you go – _open_… and –"

The _boom_ was so loud it made the floor shake. Sherlock heard it coming and grabbed onto the desk in front of him; several of the people milling about the bank looking vaguely terrified were less lucky and ended up on the ground. The Doctor stood stock still, staring at the lines of code on the screen in shock.

"_What?_" he cried, picking up the mouse and scrolling frantically through the code. "_What!_"

Sherlock straightened, letting his muscles relax after the shock of bracing for the explosion underground. "You must have typed something wrong," he said softly. He didn't intend to sound superior or gloating, but he winced to hear the notes of the emotions in his voice anyway.

"I didn't," the Doctor insisted, still scrolling up and down the screen. "It was the right command – it was the _second time_ I'd used it!"

Sherlock came up behind him and placed a consolatory hand on his shoulder. "Maybe it was just a typo. You were typing so fast, really it was impressive you got that far without one. And like I said before, it's probably better this way."

The alien watched him for a moment. "There were four Judoon down there. They'll all be dead."

He shrugged. "They weren't exactly innocent. They were trying to rob the KfW, whatever was in there could have been dangerous. It was just an accident, Doctor."

For a moment Sherlock stood there, his hand awkwardly resting on the other man's shoulder. Then the Doctor shrugged him off. "Yeah, well. Burglary of this scale is a capital offence on their planet anyway. Shame, though - I would've liked to have seen what was in there."

Sherlock snorted, although he didn't bother to attempt to deny that he had also been achingly curious. "We should probably get out of here before the police turn up," he mused, looking around at the people picking themselves up off the carpet. "_Old Atraxi_ coding accidents don't generally go down very well with the Frankfurt forces." The other man smiled in a somewhat empty sort of manner. "Do you drink coffee, Doctor?" Sherlock asked briskly.

The Doctor suddenly grinned brightly. "Coffee!" he said, clapping his hands together, quite abruptly the over-exuberant man he had been before the explosion. "I can't remember the last time I had coffee. I think I liked it. Probably about time to try it again."

Sherlock chuckled, shaking his head and leading the alien out of the bank and into the air that didn't smell like singed carpet.

"So," the Doctor said briskly when they had sat down, one hand supporting his square jaw as the other cradled a cup of coffee. "Sherlock Holmes in 21st Century Frankfurt. Something tells me you're a long way from home."

Sherlock gulped down his own coffee and grimaced at the taste: the Germans, he'd discovered, made an extraordinarily strong and bitter brew. "Yes. I have to be, really. I should really start making this my home." He gazed out of the window and sighed. Frankfurt wasn't bad, really, as far as towns went. He could get used to it.

"And…" the Doctor fiddled with his cup as though about to ask a sensitive question. "Is there a Doctor Watson around somewhere?"

Sherlock's heart spasmed. How could he know? "No. I… had to leave him behind. It wasn't… I couldn't…"

The Doctor nodded. "Oh. The Great Hiatus. I see." Sherlock didn't understand what the Great Hiatus meant, but there was such sympathy in the Doctor's big green eyes that he smiled sadly at him anyway. "So how's the hunt going, then? How many more operatives, do you think?"

It was uncanny, really, how much this man knew. "None," he said suspiciously. "I found Sebastian Moran this morning. That's why I was at the bank, I meant to collect my passports."

"Oh! Brilliant, well done you. So you can go back now?"

Sherlock blinked. "How do you know all of this?"

The Doctor started up a quick tap-tap-tap of his fingers on the table. "It's sort of… complicated. Alien-ey stuff. Time travel."

Sherlock's eyebrows shot up of their own accord. "Time travel," he repeated incredulously. The Doctor looked seriously back at him. "Right," he accepted. "So you know everything in history that's going to happen and has happened and is happening. Somehow you know who I am and you're trying to figure out whereabouts in my personal timeline I am right now?"

A sort of wheezing laugh echoed from the Doctor's mouth. "That's really cool," he said brightly. "You really are brilliant. Yeah, that's kind of what's happening. Except you are… well, you're not really supposed to be here."

"What do you mean, I'm not supposed to be here?" Sherlock asked, watching the Doctor's face carefully as he looked decidedly awkward.

"Well… it doesn't really matter. Do you need a lift back to London? I can help you with that. Always wanted to visit 221B Baker Street."

Sherlock shook his head, feeling his stomach sink. "I'm not going back to Baker Street."

The Doctor almost knocked over his coffee cup. "What? Why not?"

"John… after I 'died' he was clinically depressed for eighteen months," Sherlock tried to explain. "I put him through so much. He hated me, and himself, and it was…" he let his voice trail off before it broke and took another gulp of coffee to cover it up, but the Doctor wasn't fooled. "He's happy now. He's moved on, he's made his peace with me in his mind. If I go back now, it'll bring everything back. He'll hate me all over again, and then he'll hate himself for moving on from me when I was still out there – I can't do that to him. It's better that he just keeps thinking I'm dead."

Amazingly, the Doctor looked understanding. "But there's so much the two of you could still do together! Sherlock Holmes and Doctor Watson, your story isn't nearly over yet. He can't hate you that much. You left him a note and everything, didn't you?"

Sherlock frowned. "How could I? I didn't know what was going to happen and if I told him it wouldn't have worked. As far as he's concerned, I just killed myself."

The Doctor did drop his coffee cup this time, sending a splurge of over-milked and –sugared espresso across the tiles. "Killed yourself?" he asked, completely ignoring the stout German woman who flocked over to their table with a mop and a loud voice. "What do you mean?"

Sherlock gave him a bitter smile. "I think maybe your version of my timeline is a bit different to mine," he said dryly. "Moriarty spread rumours through the press and the police that I was a fraud. That I created crimes and then hired myself to solve them, and that's why I looked so clever. Then he cornered me on the roof of St Bart's hospital and forced me to jump off, or he was going to kill John – Doctor Watson. And Inspector Lestrade from Scotland Yard. And my landlady. I couldn't let that happen, so I jumped. I was lucky he hadn't considered Molly – a pathologist at Bart's. She patched me up and hid me until I recovered enough to leave. And I've been tracking down Moriarty's operatives ever since."

The Doctor actually reached across the table and touched his hand. "I'm sorry," he said sincerely. He turned to the waitress and smiled apologetically. "Entschuldigung sie, ich bin traurig," he told her. Sherlock, too, offered her a cursory apology. She made a sound that distinctly sounded like _about right, too_ and moved off, taking the coffee-stained mop with her. "I really am. That's awful. I know what it's like to have to leave people behind."

Sherlock awkwardly took hold of the hand resting on top of his. "I know you do. You've lost someone recently, haven't you? And they're not the first." He frowned as the other man met his eyes. "You've had a long life, us humans just can't keep up. Eventually you have to leave us behind."

The hand in his twitched as the Doctor sighed. "But the thing is, it's worth it. It might not seem it right after you leave someone, but you realise in the end that it's worth the hurt when you lose them, to have them in the first place. You and Doctor Watson, there's more. Much more. You've only just begun."

"In your version, maybe," Sherlock countered. "Right here and now, it's better this way."

"I've done it before, you know," the Doctor said finally, his fingers tapping a tarantella on the tabletop. "I know what you're going through. A while back I got into a bit of a mess with a religious group called the Silence – they – well, long story short the only way to get out of it was to fake my own death, right in front of my best friends." He looked slightly wistful for a moment. "So I ran. I ran, and I kept myself busy, and I didn't look back. I consoled myself with feeling wretched by telling myself they were better off without me."

Sherlock turned away, shifting his whole body sideways to look out of the window as though turning his face away might stop him from hearing, from feeling the John-sized hole in his chest so acutely. But the Doctor kept talking, and Sherlock kept hearing it, listening to it despite himself. "And then I met this woman, and she… convinced me to go back." Suddenly the absent frenzied tapping of fingertips on Formica stopped and the large hand grabbed at Sherlock's. "I understand how you feel," he said earnestly. Sherlock couldn't look at him because he was having trouble just _breathing_, so he blinked tears away before they could well up in his eyes and stared out of the window. "I really do, because knocking on that door was one of the hardest things I have ever done, and I've done some pretty impossible things. But it was _worth_ it. And the more I think about it the more I shudder at what the rest of my life _and theirs_ would have been like if I hadn't."

The Doctor leaned back in his chair, his hand slipping away from Sherlock's. "Of course," he said airily, looking much more like the careless man from the bank vault as a thought seemed to strike him unexpectedly, "their daughter – my wife – long story, amazing woman –" he flapped a hand unconcernedly – "she'd already told them I was still alive, so the worst I got was a squirt in the face with a water-pistol, but still."

He couldn't help but snort. "And you don't think the situation is a little different? No-one's told John I'm not dead."

"Don't you think he'd be happier with you there?" the Doctor pressed. Irritation flooded Sherlock. "What if… he's bound to find out eventually, you know he is. How do you think he'll feel when he finds out that you've been alive for years and you never told him?"

"He won't find out," Sherlock snapped. "The only people who know are Mycroft and myself." When the taller man looked unimpressed, he folded his arms defiantly across his chest. "I'm not going back."

A moment passed while the Doctor continued to stare at him, his green eyes unbelievably sad. "All right," he said finally, tugging his hand out of Sherlock's. "Mr Holmes – can I call you Sherlock?"

Sherlock smiled. "I don't know yet."

"Mr Holmes," the Doctor repeated, returning Sherlock's wry smile. He seemed entirely mad, and yet – from what he'd done at the bank he was obviously hugely intelligent. Sherlock liked him almost instinctively, but that didn't make him particularly inclined to trust him. He watched the man for a moment as he seemed to struggle with what he planned to say. "Come with me," he said finally.

Sherlock frowned. "Come with you where?"

"Wherever you like," he replied brightly. "Wherever you want to go."

He gave a hollow laugh. "I want to go home," he told him. "I'm tired and I want to go home. And I know you think a lot of yourself, _Doctor_," he said, his lip twisting, "but even you can't take me there."

The Doctor frowned. "Maybe not. But come on! Whole of time and space, wherever you want to go. Stars and planets and people you couldn't even imagine. Isn't that even a little bit tempting? What have you got here to leave behind?"

As Sherlock stared at his huge imploring eyes, he couldn't stop a tiny smile from crossing his face. "All right," he said finally, lobbing the empty coffee-cup into the bin and standing up. "Take me far away from here."

* * *

**A/N: **My updates will probably be fairly slow as I want to structure this so that each chapter stands on its own much like an episode of Doctor Who, so each chapter will be fairly long and take lots of planning, etc. This is, at the moment, my pet project. I'm having so much fun with it.

So many thanks to **CaskettFanGirl, **who is amazing and fabulous and has been there right from the beginning.

-for you!


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